The present invention relates to measuring devices and particularly to a lock mechanism of tape measure with improved characteristics.
A conventional tape measure is shown in FIG. 1 wherein the lock mechanism is implemented as below. A sliding block 12 is provided at a recess 111 in the rear of opening 11a. A flexible member 121 is formed at the front end of sliding block 12. In operation, push the sliding block 12 forward to cause flexible member 121 to move up along the engaged slope 112 for biasing against and locking tape A after tape A has been pulled out of the tape measure a desired length. Also, a cushion B is provided at the front of opening 11a for absorbing the impact of the rewinding tape A, thus protecting the tape measure.
Above tape measure is advantageous for being portable, compact, and easy operation. Thus it has been widely used in families, tailoring, and short distance measuring applications. However, user may feel laborious in locking a large tape measure incorporating above lock mechanism. This is because the length of tape is longer, the width of tape is wider, the weight of tape is heavier, and the force of the rewinding tape is much stronger. As such, simply push the sliding block 12 to cause flexible member 121 to bias against and lock tape A is not sufficient. That is why user may feel laborious in locking such large tape measure. In analyzing the cause of laboriousness, it is found that the direction of pushing the sliding block 12 to lock the tape A is opposite to that of the rewinding tape A. In other words, user has to exert a force strong enough to stop the motion of the rewinding tape for locking the tape. Further, the rewinding force of the tape of a larger tape measure is relatively strong.
It is an object of the present invention to provide a lock mechanism of tape measure comprising a case including a predetermined length of tape, a front tape opening, a bottom opening, a first and third pins at the proximal end of the tape opening, and a second pin distally from the tape opening; a lock means at the bottom opening, the lock means including a pair of rear holes with the second pin passed through and a pair of front holes; an engagement means including a planar member, an aperture in the rear of the planar member with the first pin passed through, an engagement member extended down from the aperture, a post on the planar member, and two studs on the opposite sides of the planar member received in the front holes of the lock means; and an abutment means put on the third pin above the planar member, the abutment means including an abutment member at the bottom and a spring put on the post being engaged with the abutment member. In pulling or rewinding tape, simply press the front end of control means to cause lock means to pivot upward about second pin for causing engagement means to pivot upward about first pin. At this time, spring is compressed and engagement member becomes disengaged from tape, thus allowing tape to pull or rewind freely. To the contrary, release lock means to cause both lock means and engagement means to pivot in a reverse direction by the expansion of spring until the contact member is biased against for locking tape. The locking/unlocking of tape is effected in an up-and-down movement of the front end of lock means as opposed to the transverse movement of prior art.
The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings.